Electrically controllable privacy glazing with ultralow power consumption comprising a liquid crystal material having a light transmittance that varies in response to application of an electric field

ABSTRACT

An electrically dynamic window structure may include first and second panes of transparent material and an electrically controllable optically active material positioned between the two panes. A driver can be electrically connected to electrode layers carried by the two panes. The driver may be configured to alternate between a drive phase in which a drive signal is applied to the electrode layers and an idle phase in which the drive signal is not applied to the electrode layers. The electrically controllable optically active material can maintain its transition state during the idle phase. As a result, the power consumption of the structure may be reduced as compared to if the driver continuously delivers the drive signal.

CROSS-REFERENCE

This application claims the benefit of U.S. Provisional PatentApplication No. 62/774,320, filed Dec. 2, 2018, the entire contents ofwhich are incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to structures that include an electricallycontrollable optically active material, including drivers and waveformsfor controlling the electrically controllable optically active material.

BACKGROUND

Windows, doors, partitions, and other structures having controllablelight modulation have been gaining popularity in the marketplace. Thesestructures are commonly referred to as “smart” structures or “privacy”structures for their ability to transform from a transparent state inwhich a user can see through the structure to a private state in whichviewing is inhibited through the structure. For example, smart windowsare being used in high-end automobiles and homes and smart partitionsare being used as walls in office spaces to provide controlled privacyand visual darkening.

A variety of different technologies can be used to provide controlledoptical transmission for a smart structure. For example, electrochromictechnologies, photochromic technologies, thermochromic technologies,suspended particle technologies, and liquid crystal technologies are allbeing used in different smart structure applications to providecontrollable privacy. The technologies generally use an energy source,such as electricity, to transform from a transparent state to a privacystate or vice versa.

In practice, an electrical driver may be used to control or “drive” theoptically active material. The driver may apply or cease applyingelectrical energy to the optically active material to transition betweena transparent state and privacy state, or vice versa. In addition, thedriver may apply an electrical signal to the optically active materialonce transitioned in a particular state to help maintain that state. Forexample, the driver may apply an electrical signal of alternatingpolarity to the optically active material to transition the opticallyactive material between states and/or maintain the optically activematerial in a transitioned stated. When so configured, the process ofchanging the polarity of the structure from a first polarity to a secondpolarity may require discharging the structure from a voltage down to azero voltage and then charging the structure from zero volts to anoperating voltage at the opposite polarity. This consumes electricalenergy impacting the overall energy efficiency of the structure.

SUMMARY

In general, this disclosure is directed to privacy structuresincorporating an electrically controllable optically active materialthat provides controllable privacy. The privacy structures can beimplemented in the form of a window, door, skylight, interior partition,or yet other structure where controllable visible transmittance isdesired. In any case, the privacy structure may be fabricated frommultiple panes of transparent material that include an electricallycontrollable medium between the panes. Each pane of transparent materialcan carry an electrode layer, which may be implemented as a layer ofelectrically conductive and optically transparent material depositedover the pane. The optically active material may be controlled, forexample via an electrical driver communicatively coupled to theelectrode layers, e.g., by controlling the application and/or removal ofelectrical energy to the optically active material. For example, thedriver can control application and/or removal of electrical energy fromthe optically active material, thereby causing the optically activematerial to transition from a scattering state in which visibilitythrough the structure is inhibited to a transparent state in whichvisibility through the structure is comparatively clear.

The electrical driver, which may also be referred to as a controller,may be designed to receive power from a power source, such as arechargeable and/or replaceable battery and/or wall or mains powersource. The electrical driver can condition the electricity receivedfrom the power source, e.g., by changing the frequency, amplitude,waveform, and/or other characteristic of the electricity received fromthe power source. The electrical driver can deliver the conditionedelectrical signal to electrodes that are electrically coupled to theoptically active material. In addition, in response to a user input orother control information, the electrical driver may change theconditioned electrical signal delivered to the electrodes and/or ceasedelivering electricity to the electrodes. Accordingly, the electricaldriver can control the electrical signal delivered to the opticallyactive material, thereby controlling the material to maintain a specificoptical state or to transition from one state (e.g., a transparent stateor scattering state) to another state.

In some configurations in accordance with the present disclosure, anelectrical driver is configured to transition the electricallycontrollable optically active material to a particular transition state(e.g., scattering state or clear state) and then periodically alternatethe polarity of the electrically controllable optically active materialduring a drive phase in that state. The drive can suspend driving of theelectrically controllable optically active material between polarityreversal driving episodes, and the electrically controllable opticallyactive material can hold its optical state between polarity reversaldriving episodes.

Accordingly, instead of continuously driving the electricallycontrollable optically active material while in a given transitionstate, the driver can controllably alternate between a delivery phasewhen the driver is delivering a drive signal to the electricallycontrollable optically active material and an idle phase when the driveris not delivering a drive signal to the electrically controllableoptically active material. The privacy structure containing theelectrically controllable optically active material can hold thetransition state established as of when the driver ceased deliveringpower (a drive signal) to the privacy structure over a period of timeuntil the driver again delivers a drive signal to the privacy structure.By continuously alternating between a drive phase when the driver isdelivering power (a drive signal) to the privacy structure and an idlephase when the driver is not delivering power to the privacy structure,the power consumption of the structure is reduced as compared to whenthe driver is continuously delivering power to the structure.

In some examples, the duration of the drive phase when the driver isdelivering power to the privacy structure ranges from 0.1 millisecond to10 seconds. Additionally or alternatively, the duration of the idlephase when the driver is not delivering power to the privacy structureyet the privacy structure maintains the transition state present whenthe driver ceased delivering power ranges from 1 second to 10,000seconds, such as from 1 second to 5,000 seconds, or from 300 seconds to5,000 seconds. A ratio of the duration of the idle period divided by theduration of the drive period may be greater than 1, such as from greaterthan 10, greater than 100, greater than 1000, or greater than 2500.

The duration of the idle phase for a particular privacy structure mayvary based on factors related to the quality (e.g., cleanliness) of itsinitial construction as well as transients of its environment (e.g.,size, purity, temperature, age). In general, a smaller, newer, more purepanel in a cooler climate will have a longer duration time than acomparatively larger, older, less pure panel in a hotter climate.

In some examples, the electrically controllable optically activematerial is a liquid crystal material. While a variety of differenttypes of liquid crystal materials may be used, in some applications, theliquid crystal material is a monostable liquid crystal, e.g., having oneenergetically preferred transition state. The monostable state of theliquid crystal may be a privacy (e.g., scattering) state whereas thecorresponding non-stable state of the liquid crystal may be a clearstate. In these examples, the transition state maintained by the privacyglazing structure during the idle phase can be the clear state. In otherwords, the driver can transition the liquid crystal in the privacyglazing structure from its stable state to its non-stable state (e.g.,clear state) and maintain that non-stable optical state throughalternating application of drive phases and idle phases. In anotherexample, the monostable state of the liquid crystal may be a clear statewhereas the corresponding non-stable state of the liquid crystal may bea privacy (e.g., scattering) state. In this example, the transitionstate maintained by the privacy glazing structure during the idle phasecan be the privacy state. The driver can transition the liquid crystalin the privacy glazing structure from its stable state to its non-stablestate (e.g., privacy state) and maintain that non-stable optical statethrough alternating application of drive phases and idle phases.

In some examples, the non-stable state may be desired while the privacypanel is in an idle phase or a delivery phase. To achieve the non-stablestate, the driver may externally short circuit the electrodes todischarge from an applied or working voltage down to a zero voltagestate. This discharge process may occur in less than 10 seconds from aninitial input, such as from an applied voltage of 60V or more down to 0Vin 500 milliseconds or less. If switching is desired during a drivingphase, the input applied voltage potential from the driver is firstremoved.

During each drive phase, the driver can drive the liquid crystal at afrequency and a waveform appropriate for the specific liquid crystalused. The waveform used may be an alternating current waveform, a directcurrent waveform, or a hybrid alternating current and direct currentwaveform. The waveform can have an operating amplitude and a polaritywhich, in the case of alternating current, alternates. Whentransitioning from a drive phase to an ideal phase, the drive signal canbe terminated while the waveform is at is maximum operating amplitude.The polarity of the waveform, however, will be reversed for eachsubsequent transition. For example, in the case where the privacystructure is driven with a 60 volt alternating current waveform, thedrive may initially transition from a drive phase to an idle phase whenthe current is positive 60 volts. Following a idle phase, the driver maydrive the liquid crystal for a period of time and then transition from asecond drive phase to a second idle phase when the current is negative60 volts. The driver may be physically disconnected from the opticallyactive material (e.g., by opening a switch) when transitioning from adrive phase to an idle phase.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view of an example privacy glazing structure.

FIG. 2 is a side view of the example privacy glazing structure of FIG. 1incorporated into a multi-pane insulating glazing unit.

FIG. 3 is an exemplary schematic illustration showing an exampleconnection arrangement of a driver to electrode layers of a privacystructure.

FIG. 4 shows an exemplary driver signal applied between a firstelectrode layer and a second electrode layer over time.

FIG. 5 illustrates example ion density graph data.

FIG. 6 illustrates an example hybrid waveform.

DETAILED DESCRIPTION

In general, the present disclosure is directed to electrical controlsystems, devices, and methods for controlling optical structures havingcontrollable light modulation. For example, an optical structure mayinclude an electrically controllable optically active material thatprovides controlled transition between a privacy or scattering state anda visible or transmittance state. An electrical controller, or driver,may be electrically coupled to optically active material throughelectrode layers bounding the optically active material. The electricaldriver may receive power from a power source and condition theelectricity received from the power source, e.g., by changing thefrequency, amplitude, waveform, and/or other characteristic of theelectricity received from the power source. The electrical driver candeliver the conditioned electrical signal to the electrodes. Inaddition, in response to a user input or other control information, theelectrical driver may change the conditioned electrical signal deliveredto the electrodes and/or cease delivering electricity to the electrodes.Accordingly, the electrical driver can control the electrical signaldelivered to the optically active material, thereby controlling thematerial to maintain a specific optical state or to transition from onestate (e.g., a transparent state or scattering state) to another state.

An electrical driver according to the disclosure may periodically switchthe polarity of the electricity of the delivered to the privacystructure. This periodic polarity reversal can help prevent ions withinthe electrically controllable optically active material frompreferentially migrating toward one electrode layer, which is aphenomenon sometimes referred to as ion plating. In some examples, thedriver includes hardware and/or software controlling the frequency atwhich polarity switching occurs. In operation, the driver can maintain aparticular transition state of the privacy glazing containing anelectrically controllable optically active material by alternatingbetween delivering a drive signal (power) to the electricallycontrollable optically active material and an intervening idle periodwhen no power is delivered to the electrically controllable opticallyactive material. The electrically controllable optically active materialcan function as a capacitor, holding its electrical charge during theidle period between adjacent drive periods. Accordingly, by alternatingbetween drive periods and idle periods in which no power is delivered tothe electrically controllable optically active material, the powerconsumption of the privacy structure is greatly reduced.

FIG. 1 is a side view of an example privacy glazing structure 12 thatincludes a first pane of transparent material 14 and a second pane oftransparent material 16 with a layer of optically active material 18bounded between the two panes of transparent material. The privacyglazing structure 12 also includes a first electrode layer 20 and asecond electrode layer 22. The first electrode layer 20 is carried bythe first pane of transparent material 14 while the second electrodelayer 22 is carried by the second pane of transparent material. Inoperation, electricity supplied through the first and second electrodelayers 20, 22 can control the optically active material 18 to controlvisibility through the privacy glazing structure.

Privacy glazing structure 12 can utilize any suitable privacy materialsfor the layer of optically active material 18. Further, althoughoptically active material 18 is generally illustrated and described asbeing a single layer of material, it should be appreciated that astructure in accordance with the disclosure can have one or more layersof optically active material with the same or varying thicknesses. Ingeneral, optically active material 18 is configured to providecontrollable and reversible optical obscuring and lightening. Opticallyactive material 18 can be an electronically controllable opticallyactive material that changes direct visible transmittance in response tochanges in electrical energy applied to the material.

In one example, optically active material 18 is formed of anelectrochromic material that changes opacity and, hence, lighttransmission properties, in response to voltage changes applied to thematerial. Typical examples of electrochromic materials are WO₃ and MoO₃,which are usually colorless when applied to a substrate in thin layers.An electrochromic layer may change its optical properties by oxidationor reduction processes. For example, in the case of tungsten oxide,protons can move in the electrochromic layer in response to changingvoltage, reducing the tungsten oxide to blue tungsten bronze. Theintensity of coloration is varied by the magnitude of charge applied tothe layer.

In another example, optically active material 18 is formed of a liquidcrystal material. Different types of liquid crystal materials that canbe used as optically active material 18 include polymer dispersed liquidcrystal (PDLC) materials and polymer stabilized cholesteric texture(PSCT) materials. Polymer dispersed liquid crystals usually involvephase separation of nematic liquid crystal from a homogeneous liquidcrystal containing an amount of polymer, sandwiched between electrodelayers 20 and 22. When the electric field is off, the liquid crystalsmay be randomly scattered. This scatters light entering the liquidcrystal and diffuses the transmitted light through the material. When acertain voltage is applied between the two electrode layers, the liquidcrystals may homeotropically align and the liquid crystals increase inoptical transparency, allowing light to transmit through the crystals.

In the case of polymer stabilized cholesteric texture (PSCT) materials,the material can either be a normal mode polymer stabilized cholesterictexture material or a reverse mode polymer stabilized cholesterictexture material. In a normal polymer stabilized cholesteric texturematerial, light is scattered when there is no electrical field appliedto the material. If an electric field is applied to the liquid crystal,it turns to the homeotropic state, causing the liquid crystals toreorient themselves parallel in the direction of the electric field.This causes the liquid crystals to increase in optical transparency andallows light to transmit through the liquid crystal layer. In a reversemode polymer stabilized cholesteric texture material, the liquidcrystals are transparent in the absence of an electric field (e.g., zeroelectric field) but opaque and scattering upon application of anelectric field.

In one example in which the layer of optically active material 18 isimplemented using liquid crystals, the optically active materialincludes liquid crystals and a dichroic dye to provide a guest-hostliquid crystal mode of operation. When so configured, the dichroic dyecan function as a guest compound within the liquid crystal host. Thedichroic dye can be selected so the orientation of the dye moleculesfollows the orientation of the liquid crystal molecules. In someexamples, when an electric field is applied to the optically activematerial 18, there is little to no absorption in the short axis of thedye molecule, and when the electric field is removed from the opticallyactive material, the dye molecules absorb in the long axis. As a result,the dichroic dye molecules can absorb light when the optically activematerial is transitioned to a scattering state. When so configured, theoptically active material may absorb light impinging upon the materialto prevent an observer on one side of privacy glazing structure 12 fromclearly observing activity occurring on the opposite side of thestructure.

When optically active material 18 is implemented using liquid crystals,the optically active material may include liquid crystal moleculeswithin a polymer matrix. The polymer matrix may or may not be cured,resulting in a solid or liquid medium of polymer surrounding liquidcrystal molecules. In addition, in some examples, the optically activematerial 18 may contain spacer beads (e.g., micro-spheres), for examplehaving an average diameter ranging from 3 micrometers to 40 micrometers,to maintain separation between the first pane of transparent material 14and the second pane of transparent material 16.

In another example in which the layer of optically active material 18 isimplemented using a liquid crystal material, the liquid crystal materialturns hazy when transitioned to the privacy state. Such a material mayscatter light impinging upon the material to prevent an observer on oneside of privacy glazing structure 12 from clearly observing activityoccurring on the opposite side of the structure. Such a material maysignificantly reduce regular visible transmittance through the material(which may also be referred to as direct visible transmittance) whileonly minimally reducing total visible transmittance when in the privacystate, as compared to when in the light transmitting state. When usingthese materials, the amount of scattered visible light transmittingthrough the material may increase in the privacy state as compared tothe light transmitting state, compensating for the reduced regularvisible transmittance through the material. Regular or direct visibletransmittance may be considered the transmitted visible light that isnot scattered or redirected through optically active material 18.

Another type of material that can be used as the layer of opticallyactive material 18 is a suspended particle material. Suspended particlematerials are typically dark or opaque in a non-activated state butbecome transparent when a voltage is applied. Other types ofelectrically controllable optically active materials can be utilized asoptically active material 18, and the disclosure is not limited in thisrespect.

Independent of the specific type of material(s) used for the layer ofoptically active material 18, the material can change from a lighttransmissive state in which privacy glazing structure 12 is intended tobe transparent to a privacy state in which visibility through theinsulating glazing unit is intended to be blocked. Optically activematerial 18 may exhibit progressively decreasing direct visibletransmittance when transitioning from a maximum light transmissive stateto a maximum privacy state. Similarly, optically active material 18 mayexhibit progressively increasing direct visible transmittance whentransitioning from a maximum privacy state to a maximum transmissivestate. The speed at which optically active material 18 transitions froma generally transparent transmission state to a generally opaque privacystate may be dictated by a variety of factors, including the specifictype of material selected for optically active material 18, thetemperature of the material, the electrical voltage applied to thematerial, and the like.

To electrically control optically active material 18, privacy glazingstructure 12 in the example of FIG. 1 includes first electrode layer 20and second electrode layer 22. Each electrode layer may be in the formof an electrically conductive coating deposited on or over the surfaceof each respective pane facing the optically active material 18. Forexample, first pane of transparent material 14 may define an innersurface 24A and an outer surface 24B on an opposite side of the pane.Similarly, second pane of transparent material 16 may define an innersurface 26A and an outer surface 26B on an opposite side of the pane.First electrode layer 20 can be deposited over the inner surface 24A ofthe first pane, while second electrode layer 22 can be deposited overthe inner surface 26A of the second pane. The first and second electrodelayers 20, 22 can be deposited directed on the inner surface of arespective pane or one or more intermediate layers, such as a blockerlayer, and be deposited between the inner surface of the pane and theelectrode layer.

Each electrode layer 20, 22 may be an electrically conductive coatingthat is a transparent conductive oxide (“TCO”) coating, such asaluminum-doped zinc oxide and/or tin-doped indium oxide. The transparentconductive oxide coatings can be electrically connected to a powersource, e.g., via a bus bar or other electrical connector structure. Insome examples, the transparent conductive coatings forming electrodelayers 20, 22 define wall surfaces of a cavity between first pane oftransparent material 14 and second pane of transparent material 16 whichoptically active material 18 contacts. In other examples, one or moreother coatings may overlay the first and/or second electrode layers 20,22, such as a dielectric overcoat (e.g., silicon oxynitride, siliconoxide, polyimide, silicon oxide/polyimide multilayer). In either case,first pane of transparent material 14 and second pane of transparentmaterial 16, as well as any coatings on inner faces 24A, 26A of thepanes can form a cavity or chamber containing optically active material18.

When a dielectric overcoat is used, the dielectric overcoat (be itformed of a single layer or multiple layers) may have a dielectricconstant greater than 2, such as greater than 5, or greater than 10.Additionally or alternatively, the dielectric overcoat may have adielectric strength of greater than 3×10⁵ (volts/centimeter), such asgreater than 3×10⁷ (V/cm) and a dielectric loss less than 0.05, such asless than 0.03, or less than 0.01. The dielectric overcoat could besputtered deposited or applied as a coated film.

The panes of transparent material forming privacy glazing structure 12,including first pane 14 and second pane 16, can be formed of anysuitable material. Each pane of transparent material may be formed fromthe same material, or at least one of the panes of transparent materialmay be formed of a material different than at least one other of thepanes of transparent material. In some examples, at least one (andoptionally all) the panes of privacy glazing structure 12 are formed ofglass. In other examples, at least one (and optionally all) the privacyglazing structure 12 are formed of plastic such as, e.g., a fluorocarbonplastic, polypropylene, polyethylene, or polyester. When glass is used,the glass may be aluminum borosilicate glass, sodium-lime (e.g.,sodium-lime-silicate) glass, or another type of glass. In addition, theglass may be clear or the glass may be colored, depending on theapplication. Although the glass can be manufactured using differenttechniques, in some examples the glass is manufactured on a float bathline in which molten glass is deposited on a bath of molten tin to shapeand solidify the glass. Such an example glass may be referred to asfloat glass.

In some examples, first pane 14 and/or second pane 16 may be formed frommultiple different types of materials. For example, the substrates maybe formed of a laminated glass, which may include two panes of glassbonded together with a polymer such as polyvinyl butyral. Additionaldetails on privacy glazing substrate arrangements that can be used inthe present disclosure can be found in US Patent Publication No.US2018/0307111, titled “HIGH PERFORMANCE PRIVACY GLAZING STRUCTURES” andfiled Apr. 20, 2018, the entire contents of which are incorporatedherein by reference. In addition, further details on driver hardwareand/or software that can be used with privacy glazing arrangementsaccording to the present disclosure can be found in in US PatentPublication No. US2019/0346710, titled “ELECTRICALLY CONTROLLABLEPRIVACY GLAZING WITH ENERGY RECAPTURING DRIVER” and filed May 9, 2019,the entire contents of which are incorporated herein by reference.

Privacy glazing structure 12 can be used in any desired application,including in a door, a window, a wall (e.g., wall partition), a skylightin a residential or commercial building, or in other applications. Tohelp facilitate installation of privacy glazing structure 12, thestructure may include a frame 30 surrounding the exterior perimeter ofthe structure. In different examples, frame 30 may be fabricated fromwood, metal, or a plastic material such a vinyl. Frame 30 may define achannel 32 that receives and holds the external perimeter edge ofstructure 12. The sightline through privacy glazing structure 12 isgenerally established as the location where frame 30 end and visibilitythrough privacy glazing structure 12 begins.

In the example of FIG. 1, privacy glazing structure 12 is illustrated asa privacy cell formed of two panes of transparent material boundingoptically active material 18. In other configurations, privacy glazingstructure 12 may be incorporated into a multi-pane glazing structurethat include a privacy cell having one or more additional panesseparated by one or more between-pane spaces. FIG. 2 is a side view ofan example configuration in which privacy glazing structure 12 from FIG.1 is incorporated into a multi-pane insulating glazing unit having abetween-pane space.

As shown in the illustrated example of FIG. 2, a multi-pane privacyglazing structure 50 may include privacy glazing structure 12 separatedfrom an additional (e.g., third) pane of transparent material 52 by abetween-pane space 54, for example, by a spacer 56. Spacer 56 may extendaround the entire perimeter of multi-pane privacy glazing structure 50to hermetically seal the between-pane space 54 from gas exchange with asurrounding environment. To minimize thermal exchange across multi-paneprivacy glazing structure 50, between-pane space 54 can be filled withan insulative gas or even evacuated of gas. For example, between-panespace 54 may be filled with an insulative gas such as argon, krypton, orxenon. In such applications, the insulative gas may be mixed with dryair to provide a desired ratio of air to insulative gas, such as 10percent air and 90 percent insulative gas. In other examples,between-pane space 54 may be evacuated so that the between-pane space isat vacuum pressure relative to the pressure of an environmentsurrounding multi-pane privacy glazing structure 50.

Spacer 56 can be any structure that holds opposed substrates in a spacedapart relationship over the service life of multi-pane privacy glazingstructure 50 and seals between-pane space 54 between the opposed panesof material, e.g., so as to inhibit or eliminate gas exchange betweenthe between-pane space and an environment surrounding the unit. Oneexample of a spacer that can be used as spacer 56 is a tubular spacerpositioned between first pane of transparent material 14 and third paneof transparent material 52. The tubular spacer may define a hollow lumenor tube which, in some examples, is filled with desiccant. The tubularspacer may have a first side surface adhered (by a first bead ofsealant) to the outer surface 24B of first pane of transparent material14 and a second side surface adhered (by a second bead of sealant) tothird pane of transparent material 52. A top surface of the tubularspacer can exposed to between-pane space 54 and, in some examples,includes openings that allow gas within the between-pane space tocommunicate with desiccating material inside of the spacer. Such aspacer can be fabricated from aluminum, stainless steel, athermoplastic, or any other suitable material.

Another example of a spacer that can be used as spacer 56 is a spacerformed from a corrugated metal reinforcing sheet surrounded by a sealantcomposition. The corrugated metal reinforcing sheet may be a rigidstructural component that holds first pane of transparent material 14apart from third pane of transparent material 52. In yet anotherexample, spacer 56 may be formed from a foam material surrounded on allsides except a side facing a between-pane space with a metal foil. Asanother example, spacer 56 may be a thermoplastic spacer (TPS) spacerformed by positioning a primary sealant (e.g., adhesive) between firstpane of transparent material 14 and third pane of transparent material52 followed, optionally, by a secondary sealant applied around theperimeter defined between the substrates and the primary sealant. Spacer56 can have other configurations, as will be appreciated by those ofordinary skill in the art.

Depending on the application, first patent of transparent material 14,second pane of transparent material 16, and/or third pane of transparentmaterial 52 (when included) may be coated with one or more functionalcoatings to modify the performance of privacy structure. Examplefunctional coatings include, but are not limited to, low-emissivitycoatings, solar control coatings, and photocatalytic coatings. Ingeneral, a low-emissivity coating is a coating that is designed to allownear infrared and visible light to pass through a pane whilesubstantially preventing medium infrared and far infrared radiation frompassing through the panes. A low-emissivity coating may include one ormore layers of infrared-reflection film interposed between two or morelayers of transparent dielectric film. The infrared-reflection film mayinclude a conductive metal like silver, gold, or copper. Aphotocatalytic coating, by contrast, may be a coating that includes aphotocatalyst, such as titanium dioxide. In use, the photocatalyst mayexhibit photoactivity that can help self-clean, or provide lessmaintenance for, the panes.

The electrode layers 20, 22 of privacy glazing structure 12, whetherimplemented alone or in the form of a multiple-pane structure with abetween-pane space, can be electrically connected to a driver. Thedriver can provide power and/or control signals to control opticallyactive material 18. In some configurations, wiring is used to establishelectrical connection between the driver and each respective electrodelayer. A first wire can provide electrical communication between thedriver and the first electrode layer 20 and a second wire can provideelectrical communication between the driver and the second electrodelayer 22. In general, the term wiring refers to any flexible electricalconductor, such as a thread of metal optionally covered with aninsulative coating, a flexible printed circuit, a bus bar, or otherelectrical connector facilitating electrical connection to the electrodelayers.

FIG. 3 is a schematic illustration showing an example connectionarrangement between a driver and electrode layers of a privacystructure. In the illustrated example, wires 40 and 42 electricallycouple driver 60 to the first electrode layer 20 and the secondelectrode layer 22, respectively. In some examples, wire 40 and/or wire42 may connect to their respective electrode layers via a conduit orhole in the transparent pane adjacent the electrode layer. In otherconfigurations, wire 40 and/or wire 42 may contact their respectiveelectrode layers at the edge of the privacy structure 12 withoutrequiring wire 40 and/or wire 42 to extend through other sections (e.g.,transparent panes 14, 16) to reach the respective electrode layer(s). Ineither case, driver 60 may be electrically coupled to each of electrodelayers 20 and 22.

In operation, the driver 60 can apply a voltage difference betweenelectrode layers 20 and 22, resulting in an electric field acrossoptically active material 18. The optical properties of the opticallyactive material 18 can be adjusted by applying a voltage across thelayer. In some embodiments, the effect of the voltage on the opticallyactive material 18 is independent on the polarity of the appliedvoltage. For example, in some examples in which optically activematerial 18 comprises liquid crystals that align with an electric fieldbetween electrode layers 20 and 22, the optical result of the crystalalignment is independent of the polarity of the electric field. Forinstance, liquid crystals may align with an electric field in a firstpolarity and may rotate approximately 180° in the event the polarity ifreversed. However, the optical state of the liquid crystals (e.g., theopacity) in either orientation may be approximately the same.

FIG. 4 shows an example alternating current drive signal that may beapplied between first electrode layer 20 and second electrode layer 22over time. It will be appreciated that the signal of FIG. 4 is exemplaryand is used for illustrative purposes, and that any variety of signalsapplied from the driver may be used. In the example of FIG. 4, a voltagesignal between the first electrode layer and the second electrode layerproduced by the driver varies over time between applied voltages V_(A)and −V_(A). In other words, in the illustrated example, a voltage ofmagnitude V_(A) is applied between the first and second electrodelayers, and the polarity of the applied voltage switches back and forthover time. The optical state (e.g., either transparent or opaque) ofoptically active layer 18 may be substantially unchanging while thevoltage is applied to the optically active layer even though the voltageapplied to the layer is varying over time. The optical state may besubstantially unchanging in that the unaided human eye may not detectchanges to optically active layer 18 in response to the alternatingpolarity of the current. However, optically active layer 18 may changestate (e.g., from transparent to opaque) if the driver stops deliveringpower to the optically active layer.

As shown in the example of FIG. 4, the voltage does not immediatelyreverse polarity from V_(A) to −V_(A). Instead, the voltage changespolarity over a transition time 70 (shaded). In some examples, asufficiently long transition time may result in an observable transitionof the optically active material between polarities. For instance, in anexemplary embodiment, liquid crystals in an optically active materialmay align with an electric field to create a substantially transparentstructure and become substantially opaque when the electric field isremoved. Thus, when transitioning from V_(A) (transparent) to −V_(A)(transparent), a slow enough transition between V_(A) and −V_(A) mayresult in an observable optical state (e.g., opaque or partially opaque)when −V_(A)<V<V_(A) (e.g., when |V|<<V_(A)). On the other hand, a fastenough transition between polarities (e.g., from V_(A) to −V_(A)) mayappear to an observer (e.g., to the naked eye in real time) to result inno apparent change in the optical state of the optically activematerial.

In some examples, if a particular optical state (e.g., a transparentstate) is to be maintained, switching between polarities that eachcorrespond to that optical state (e.g., between +V_(A) and −V_(A)) canprevent damage to the optically active material. For example, in somecases, a static or direct current voltage applied to an optically activematerial can result in ion plating within the structure, causing opticaldefects in the structure. To avoid this optical deterioration, a driverfor an optically active material (e.g., in an electrically dynamicwindow such as a privacy structure) can be configured to continuouslyswitch between applied polarities of an applied voltage (e.g. V_(A)) inorder to maintain the desired optical state.

In accordance with some examples of the present disclosure, driver 60can control the privacy glazing structure 12 to maintain a given opticalstate (e.g., clear state or privacy state) by alternating between adrive phase and an idle phase. During each drive phase, driver 60 candeliver power via a drive signal to first and second electrode layers20, 22. During each idle phase, driver 60 can suspend (e.g., ceasedelivering power) to first and second electrode layers 20, 22. Opticallyactive layer 18 can maintain its transition state during each idlephase.

To allow optically active layer 18 to maintain its transition stateduring each idle phase, privacy glazing structure 12 and opticallyactive layer 18 may be selected and fabricated to have a high voltageholding ratio (VHR). In general, VHR is a measure of the time privacyglazing structure 12 and, more particularly optically active layer 18,transitions from clear to scatter (or vice versa) after voltage isremoved. In some examples, privacy glazing structure 12 and/or opticallyactive layer 18 exhibit a VHR of at least 50%, such as at least 75%, orat least 90%.

During or after fabrication of privacy glazing structure 12, the VHR ofthe structure may be measured and the applied voltage (V_(A)) and/orduration of the idle period selected for controlling the structure maybe determined based on measured VHR. For example, the applied voltage(V_(A)) may be increased to allow for a nominal voltage loss during theidle phase. Privacy glazing structure 12 may be characterized as havinga threshold voltage (V_(threshold)) below which optically active layer18 transitions from one state to a different state. The applied voltage(V_(A)) delivered may be greater than 120% of V_(threshold) (V_(A)>1.2V_(threshold)), such as greater than 150% of V_(threshold)(V_(A)>1.5V_(threshold)), or greater than 200% of V_(threshold)(V_(A)>2V_(threshold)).

For example, driver 60 may be configured to periodically measure the VHRof privacy glazing structure 12 and adjust the applied voltage and/orduration of the idle period based on the measured VHR. Driver 60 mayperiodically sample the floated voltage at a time period just prior todischarging the panel. Each measured sample may incur a penalty orburdened voltage, which may be minimized using a low current sensemethod.

In some examples, driver 60 delivers a hybrid waveform during each drivephase that can be the main waveform or ultra-low power waveform. Thehybrid waveform may include an AC pulse (e.g., square), a continuous DCpulse, and zero-power state or physical-disconnect state (or relaystate), which is referred to also as the idle phase. The AC pulse may beis used to mitigate accumulation of impurities in the liquid crystalmedium while maintaining the ON state of the appliance. The DC pulse maybe is used to minimize power consumption as well as to let the ON stateof the appliance to stabilize from any electrical and or opticalinstabilities. The idle phase can be used to achieve maximum powersavings.

For continuous operation of the smart window, the hybrid waveform isapplied repeatedly. By changing the amount of time each electricalelement applied, the appliance can operate at very low power levels.

FIG. 5 shows an example 14 inch×20 inch smart window capable ofoperating using the above-disclosed hybrid waveform. The top graphrepresents the ion density graph where the ion density measurementprovides a panel resistance of about 380 megohms and voltage holdingratio from the VHR measurement is 95.16%. However, when the 14 inch×20inch appliance shows resistance and voltage holding ratios in the onemegohm range and 30% range respectively, the quality of the appliancemay not be appropriate to utilize the hybrid waveform. Ultra low powerwaveform is generally applicable to privacy appliances, e.g.,characterized by high resistance and high voltage holding ratio. For a14 inch×20 inch privacy appliance, high resistance and a high voltageholding ratio may be in the range of at least ten of megohm resistanceand at least 40%, respectively.

FIG. 6 illustrates an example hybrid waveform where X, Y and Z representAC, DC and No-powered signal elements.

In some embodiments, a driver for driving an optically active materialcan include a controller configured to adjust operation of one or moreswitching mechanisms in a switching network and/or to adjust the voltageapplied to the switching mechanisms. In some examples, the controlleroperates in response to an input from a user interface, such as acommand from a user interface to change the optical state of theoptically active material.

In various examples, the controller can include one or more componentsconfigured to process received information, such as a received inputfrom a user interface, and perform one or more corresponding actions inresponse thereto. Such components can include, for example, one or moreapplication specific integrated circuits (ASICs), microcontrollers,microprocessors, field-programmable gate arrays (FPGAs), or otherappropriate components capable of receiving and output data and/orsignals according to a predefined relationship. In some examples, suchone or more components can be physically integrated with the otherdriver components, such as the switching network and the like.

A user interface in communication with the controller can include aswitch or other component in wired or wireless communication with thecontroller. For instance, a hard switch (e.g., a wall switch proximatean optically dynamic window structure) can be coupled to the controllerand can switch between two or more switching states, each correspondingto an optical state of the controller optically active material.Additionally or alternatively, the driver may be configured tocommunicate with an external component, such as a smartphone or tabletvia wireless communication or an internet-connected device (e.g.,through a hard-wired or wireless network connection). In someembodiments, the controller can receive a signal from such an externaldevice corresponding to a desired optical state of the optically activematerial, and can control the optically active material accordingly.

Various examples have been described. These and other examples arewithin the scope of the following claims.

The invention claimed is:
 1. An electrically dynamic window structurecomprising: a first pane of transparent material; a second pane oftransparent material; an electrically controllable optically activematerial positioned between the first pane of transparent material andthe second pane of transparent material, the electrically controllableoptically active material being positioned between a first electrodelayer and a second electrode layer, the electrically controllablyoptically active material having a first optical transition state and asecond optical transition state, wherein the electrically controllablyoptically active material is a liquid crystal material having a lighttransmittance that varies in response to application of an electricalfield; and a driver electrically connectable to the first electrodelayer and the second electrode layer, wherein the driver configured toalternate between a drive phase in which a drive signal is applied tothe first electrode layer and the second electrode layer to drive theelectrically controllable optically active material to the first opticaltransition state and an idle phase in which the drive signal is notapplied to the first electrode layer and the second electrode layer yetthe electrically controllable optically active material maintains thefirst optical transition state.
 2. The structure of claim 1, wherein thedriver is configured execute each idle phase for a period ranging from 1second to 5000 seconds between each drive phase.
 3. The structure ofclaim 1, wherein the driver is configured to execute each drive phasefor a period ranging from 1 milliseconds to 10 seconds.
 4. The structureof claim 1, wherein the driver is configured execute the drive phase fora duration and the idle phase for a duration such that a ratio of theduration of the idle phase divided by the duration of the drive phase isgreater than
 1. 5. The structure of claim 4, wherein the ratio isgreater than
 10. 6. The structure of claim 4, wherein the ratio isgreater than
 100. 7. The structure of claim 1, wherein the electricallycontrollable optically active material exhibits a voltage holding ratioof at least 50%.
 8. The structure of claim 1, wherein the electricallycontrollable optically active material exhibits a voltage holding ratioof at least 90%.
 9. The structure of claim 1, wherein the liquid crystalmaterial is monostable, having a stable transition state and anon-stable transition state, and the first optical transition state isthe non-stable transition state.
 10. The structure of claim 9, whereinthe non-stable transition state is a privacy state.
 11. The structure ofclaim 9, wherein the non-stable transition state is a clear state. 12.The structure of claim 1, wherein the driver is configured to receivepower from a power source, generate a conditioned electrical signal, andsupply the conditioned electrical signal to the first electrode layerand the second electrode layer, the power source being wall powerdelivering alternating current.
 13. The structure of claim 1, whereinthe driver is configured to receive power from a power source, generatea conditioned electrical signal, and supply the conditioned electricalsignal to the first electrode layer and the second electrode layer, thepower source being a battery.
 14. The structure of claim 1, wherein thedriver comprises a controller that is configured to receive input from auser control located outside of the electrically dynamic windowstructure.
 15. The structure of claim 1, wherein the first pane oftransparent material and the second pane of transparent material areeach fabricated from float glass.
 16. The structure of claim 1, whereinthe first electrode layer comprises a transparent conductive oxidecoating deposited over the first pane of transparent material and thesecond electrode layer comprises a transparent conductive oxide coatingdeposited over the second pane of transparent material.
 17. Thestructure of claim 1, further comprising a dielectric overcoatoverlaying at least one of the first electrode layer and the secondelectrode layer.
 18. The structure of claim 17, wherein the dielectricovercoat has a dielectric strength of greater than 3×10⁵volts/centimeter.
 19. The structure of claim 17, wherein the dielectricovercoat comprises silicon oxide.
 20. The structure of claim 1, furthercomprising: a third pane of transparent material; and a spacerseparating the third pane of transparent material from the first pane oftransparent material and defining a sealed gas space therebetween.